Libya's Petroleum Facilities Guards Wednesday said four of its members were killed the previous night in an attack by armed extremists on al-Mabruk oilfield in central Libya.

Libya National Oil Corporation (NOC) confirmed the attack in a statement, saying "the attack took place Tuesday on al-Mabruk oilfield, 170 km south of the city of Sirte, by unidentified armed force", Xinhua news agency reported.

The corporation also explained that after the attack, "the workers of the field evacuated the place and reached Sirte unharmed".

Al-Mabruk oilfield has been shut down due to declared force majeure on Sidra oil port at the end of last year. Only a minimum number of personnel were present in the field.

"Since the workers' withdrawal, we have no longer any communications with the field, nor any information about possible damage," the statement said.

"At a time when the national oil corporation regrets what happened in al-Mabruk oilfield, we hope that the competent authorities initiate investigation on this attack, identify the offenders, and bring them to justice," it added.

Mohammed Al-Hrari, spokesman for the corporation, told Xinhua that none of the field's workers have been kidnapped during the attack.

The oilfield is located in Libya's central province of Jufrah, some 650 km southeast of Tripoli. It is run by NOC and France's Total.

Since the 2011 downfall of former Libyan leader Muammar Gaddafi, the Middle East nation, a major oil-producer of the Organization of the Petroleum Exporting Countries (OPEC), has been plagued with armed clashes, kidnappings and assassinations.